Much concerning a theory which relates brain size, DHEA, testosterone
and human evolution.

Darwinians, myself included, will have a hard time taking this theory
seriously. What is selected for directly is not hormone levels or
brain size, but behavior. Any given behavior is likely to be
influenced by many biochemical factors, not just a few as implied by
Mr. Howard's argument.
In particular, it is implausible that changes in brain size over a
number of different hominid species can be attributed to the global
effects of the same few hormones for a series of different hominids.
Also any evolutionary increase in brain size is likely to be due to a
selective pressure for some critical behaviors, which may be
facilitated by the increase in the size to those parts of the brain
which affect that behavior. The size of the brain is a very crude
evolutionary measure.
A more promising approach to understanding hominid evolution is
detailed by Steven Mithin, in his recent book, _Prehistory of the
Mind_, which I am in the process of reading. The "mind" Mithin is
talking about is the human mind. He attempts to deduce the changes in
behavior of hominids from archaeological evidence, which he reasons
reflect the development of specific parts of the brain, e.g., for
"social intelligence", "natural history intelligence", "technical
intelligence", etc. It is his thesis that these "intelligences"
developed one at a time. For example, he argues that Neanderthals had
an undeveloped "technical intelligence", that is they were unable to
conceive of complex tools.